While that might work as a gadget play once I don't understand the reasoning behind using a 300 pounder as a receiver. NFL defenses will figure out a way to defend it immediately.
To repeat, the idea is to use that 300 lb. TE in the short yardage 7-man line in place of a blocking TE., with a better execution profile as illustrated below
The question might be, "why bother?" Why not just carry a 3rd. TE with blocking credentials? It's simple...to open up an additional spot on the 53-man roster and, perhaps more importantly, the 45-man game day roster. In the previously presented scenario, those roster spots were allocated to a guy like M-B.
I am indifferent as to what spot a guy like M-B would occupy on the depth chart. If one is more comfortable showing him as the #3 TE on the depth chart with 6 others filling out the WR spots and a guy like Spriggs show simply as "OT", instead of showing 2 TEs, a guy like Spriggs as "OT/TE", along with 7 WRs, go ahead.
In the process, you get better run blocking from an OT than a TE when the short yardage play is a run, something the Packers could certainly use with that lousy 3rd. and short run performance the last couple of years. If that OT-as-TE can execute a simple pass play...chip, release into the flat, turn, catch the ball...when the defense gives it to you, net-net you get more than you'd get from a short yardage blocking TE and add an extra roster spot in the bargain.
So, you don't want just any OT in that role; you want somebody who presents at least a
threat to catch the ball in short yardage so the opponent does not sell out on the run from that side, and if they don't respect the pass catching threat, then the OT-at-TE needs to be able to
execute the route and catch.
As I said, the way to present that pass threat is to get at least one catch on tape. If an opponent respects that threat, then the OT-as-TE presents an improvement in the run game. If an opponent shows no tendency to respect that threat early in a game, selling out on the run, you would want to have a play and a player to execute a route and catch later in the game.
I think we've established that Spriggs never caught a ball in college, and perhaps never in high school. However, when he came to Indiana at 265 lbs., making him a TE was evidently a consideration, so you'd think he has sufficient athleticism to execute a short route and catch.